Initial commit

README.md

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+# ChrisKaczor.Wpf.Application.SingleInstance
+
+This library can be used to restrict an application to only a single instance and sends the command line of any newly started instance to the currently running instance.
+
+## Authors
+
+* **Chris Kaczor** - *Initial work* - https://github.com/ckaczor - https://chriskaczor.com
+
+## License
+
+This project is licensed under the MIT License - see the [LICENSE.md](LICENSE.md) file for details.
+
+## Disclaimer
+
+This code is used by my various personal projects and may not be useful or work in all use cases.

SingleInstance.cs

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+using H.Pipes;
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace ChrisKaczor.Wpf.Application
+{
+    public static class SingleInstance
+    {
+        public static event EventHandler<string> MessageReceived = delegate { };
+
+        private static PipeServer<string>? _pipeServer;
+        private static SynchronizationContext? _syncContext;
+
+        public static async Task<IDisposable?> GetSingleInstanceHandleAsync(string applicationName)
+        {
+            // Create the mutex and see if it was newly created
+            var mutex = new Mutex(false, applicationName, out var createdNew);
+
+            // Return the mutex if it was created
+            if (createdNew) return mutex;
+
+            // Create a client to send to the other instance
+            await using var pipeClient = new PipeClient<string>(applicationName);
+
+            try
+            {
+                // Connect to the other instance
+                await pipeClient.ConnectAsync(new CancellationTokenSource(500).Token);
+
+                // Send the command line to the other instance
+                await pipeClient.WriteAsync(Environment.CommandLine);
+            }
+            catch (Exception)
+            {
+                // Ignored
+            }
+
+            return null;
+        }
+
+        public static async Task StartAsync(string applicationName)
+        {
+            // Store the synchronization context of the current thread
+            _syncContext = SynchronizationContext.Current;
+
+            _pipeServer = new PipeServer<string>(applicationName);
+
+            _pipeServer.MessageReceived += PipeServer_MessageReceived;
+
+            await _pipeServer.StartAsync();
+        }
+
+        public static async Task Stop()
+        {
+            if (_pipeServer == null) return;
+
+            await _pipeServer.StopAsync();
+        }
+
+        private static void PipeServer_MessageReceived(object? sender, H.Pipes.Args.ConnectionMessageEventArgs<string?> e)
+        {
+            // Fire the event on the original thread
+            _syncContext?.Send(_ => MessageReceived(null, e.Message!), null);
+        }
+    }
+}

Wpf.Application.SingleInstance.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+	<PropertyGroup>
+		<TargetFramework>net7.0-windows</TargetFramework>
+		<Nullable>enable</Nullable>
+		<UseWPF>true</UseWPF>
+		<RootNamespace>ChrisKaczor.Wpf.Application</RootNamespace>
+		<Title>ChrisKaczor.Wpf.Application.SingleInstance</Title>
+		<Authors>Chris Kaczor</Authors>
+	</PropertyGroup>
+	<ItemGroup>
+	  <PackageReference Include="H.Pipes" Version="2.0.47" />
+	</ItemGroup>
+</Project>

Wpf.Application.SingleInstance.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.5.33516.290
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Wpf.Application.SingleInstance", "Wpf.Application.SingleInstance.csproj", "{6A5FBB13-4B83-4F7D-84CC-9474711100EA}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{6A5FBB13-4B83-4F7D-84CC-9474711100EA}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{6A5FBB13-4B83-4F7D-84CC-9474711100EA}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{6A5FBB13-4B83-4F7D-84CC-9474711100EA}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{6A5FBB13-4B83-4F7D-84CC-9474711100EA}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {9AF9F429-2093-4B89-96EB-C55EFBFD6EDD}
+	EndGlobalSection
+EndGlobal